An inertial measurement unit (“IMU”) is an electronic device that, using at least one accelerometer or gyroscope, measures and reports such parameters as velocity, orientation, and/or gravitational force. Some vehicles, such as ones that operate outside the range of a global-positioning system (“GPS”), use an on-board IMU to measure these parameters and determine, for example, the vehicle's speed, acceleration, orientation, position, and/or direction of movement. Vehicles used for high-availability or life-critical systems may employ a fault-tolerant IMU system, for example one that uses multiple IMUs to protect against the failure of a single IMU. Typically, fault-tolerant IMU systems use three or more IMUs to detect the failure of an IMU and isolate the failing IMU from the other, functional IMUs. For example, two or more similar IMUs having similar outputs will vote out a third failed IMU having a dissimilar output.
A fault-tolerant system having multiple IMUs, however, generally pays an associated mass, power, and volume (“M/P/V”) penalty for each additional IMU. Some vehicles, such as satellites or spacecraft, value M/P/V very highly, and the M/P/V of three IMUs may present a prohibitively high barrier to cost-effective launch and operation of the vehicle. Furthermore, the cost of each IMU itself may render a traditional fault-tolerant IMU system financially untenable. A need therefore exists for a fault-tolerant IMU design with less mass, power consumption, volume, and/or cost.